Leather making implicates use of large quantities of water, for conversion of raw hides and skins into finished leather. Typically in leather processing the preserved hides and skins are treated with water initially to rehydrate the skins. Subsequently they are treated with lime and sulfide or enzyme to facilitate removal of the hair and flesh adhering to the skins. The material at this stage is called limed pelt. These pelts are then processed in wooden drums using water as the medium of processing. The pelts are treated with acid salts to remove residual lime and short hairs present in an operation called deliming and bating. The operation employs about 2-3 L of water per kilo of pelt. The medium is then discharged as effluent. Sometimes, degreasing for removal of excess fat is also carried out along with deliming and bating. Subsequently the pelts are treated with 1-2 L of water per kilo of pelt along with salt and acid to condition to a pH of 2.5-2.8 from the pelt pH of about 8.0. This operation is called pickling. The used medium is again discharged as effluent rich in salinity. The pickled pelts are then treated with about 2-3 L of water per kilo of material along with 8% chromium based tanning agent and mixture of alkalis in a process called chrome tanning. The material obtained at the end of chrome tanning is called “Wet blue leather”. The pH of the leather will be in the range of 3.8-4.0.
The pelts are sometimes treated with vegetable tannins instead of chromium. The leathers obtained through such process are called vegetable tanned leathers.
Essentially all these operations employ water as medium in drums to produce leathers of defined quality. Globally, this remains practice of leather making and for conversion of one kilo of pelt to tanned leathers nearly 5-6 L of water is employed which includes intermittent washing of leathers between the various operations.
While on one side need for water poses serious availability problem and since most of the water is discharged as effluent, treatment of the large quantity of effluent with all residual chemicals is another major environmental challenge. Nearly 30,000 Tonnes of hides and skins are processed per day globally leading to use of about 150-200 million liters of water on daily basis. The same quantity of water with high salinity, chromium residues and other unutilized chemicals need to be treated as effluent every day. Such practices have threatened the sustainability of leather making.
Efforts are being made to avoid use of water in leather processing. Our co-pending patent (0085/DEL/2014) deals with a tanning composition for water free pickle free tanning. This requires Basic Chromium Sulphate (BCS) as an ingredient for tanning composition preparation, limiting the scope for wide manufacturing and application. Further it is applicable only for chrome tanning and not for vegetable tanning.
Thus, keeping in view the drawbacks of the hitherto reported prior art the inventors of the present invention realized that there exists a dire need to provide a composition that obviates the above limitations and ensures that the tanning process is executed without using water or any other medium as done in conventional processes.